The vast majority of people deported from inside the United States have been convicted of crimes, a new study shows, while those caught crossing the border illegally are being removed almost immediately with "limited due process or screening to establish their histories," The New York Times reports.

The study by Washington’s nonpartisan Migration Policy Institute (MPI) shines a light on the Obama administration’s policies and procedures concerning immigration enforcement. In five years, the current administration has deported 1.9 million people, nearly the same number — 2 million — during the eight years President George W. Bush was in office.

The study finds that illegal immigrants trying to enter at the border receive much different treatment than those who are already here, an accusation Republicans have lodged at the president, accusing him of "gutting interior enforcement and allowing the Secure Communities program to bypass too many immigrants who are here illegally," according to the Times.

The Secure Communities concept, according to U.S. Immigration and Customs Enforcement, prioritizes removing "criminal aliens" and repeat immigration violators, while not placing any additional burden on state and local law enforcement. Through shared fingerprint images in an FBI database, the Department of Homeland Security – and not state or local law enforcement – takes enforcement action.

Three-quarters of immigrants deported through the Secure Communities program had been convicted of crimes, according to the MPI report, which noted many were immigration-related offenses, such as illegally crossing the border or evading a prior deportation order.

Conversely, according to the Times, of the 530,019 people flagged for being in the United States illegally in 2013, 85 percent were not deported, mostly because they did not have a criminal record.

Immigrant groups have protested the volume of deportations during the Obama administration, resulting in the White House reviewing interior enforcement policies, but holding to its aggressive border security policy.

Immigrant advocates maintain that established communities of "unauthorized immigrants" are subjected to living in fear of being deported.

According to the MPI report, "more humane enforcement is fundamentally in tension with stricter immigration control; and that a more robust enforcement system inevitably inflicts damage on established families and communities."

Last month, the White House announced a review of immigration enforcement policies to see if it could be done "more humanely within the confines of the law." The announcement came after the president met with leaders of the Congressional Hispanic Caucus following outrage by Hispanic and immigrant groups angry about the high numbers of deportations. One leader dubbed President Barack Obama "deporter-in-chief."